I have mine flashed with a Kit-Kat rom and it is smooth and fast even though Google has given up support for it. I have the GSM Version on T-mobile and it is fast and and reliable. The battery life is pretty good with the rom and kernel combo i'm using. It has the Nexus 5 feel and experience. I will be keeping this phone til I either loose or break it or it dies. The battery is removable but there is no expandable memory. It has internal 16GB of memory which I think is plenty since there really isnt much need to store music on the phone. Google Play Music stores all your music on the cloud for free. I like that the charging and headphone ports are on the bottom of the phone together. It sucks having a phone where you have a wire sticking out of it on both the top and bottom. Having them both side by side on the bottom is better. The external speaker is clear and loud if need be. It has a forward facing camera for hangouts or skyping and an indicator LED for messages. The phone has not failed me yet and I would recommend to anyone. Battery Life Good battery life with the right rom. I had mine go two days from full charge to almost dead before. Display/Screen Quality The OLED screen is so nice, the main reason I am sticking with Samsung phones. The blacks are as dark as they get. Call Quality Same as any other phone I suppose. Ease of Use Button placement is perfect and screen is very responsive. Durability I dont used a case and this thing has no scratches yet. Design A Very sexy phone. Love the curved glass and the textured back.